DEM-CFD analysis of contact electrification and electrostatic interactions during fluidization

Abstract

Contact electrification and electrostatic interactions often occur in the fluidization process, which can significantly influence the dynamic behaviour of particles and the fluidization performance. In this study, a discrete element method coupled with computational fluid dynamics (DEM-CFD) is developed by implementing contact electrification and electrostatic interaction models and the combined effects of contact electrification and electrostatic interaction on fluidization are analysed. It is found that the charge of the particle system increase with the superficial gas velocity. Particles of different material properties (especially work function) can be bi-charged and form agglomerates. At low superficial gas velocities, the particle bed cannot be fully fluidized and the pressure drop tends to be stable rather than fluctuating as the gas flows through the micro-channels of agglomerates. However, at high superficial gas velocities, the agglomerates can break, inducing strong fluctuation of pressure drop. Clearly, the electrostatic phenomena and fluidization behaviour can mutually influence each other during the process

Experimental and numerical study of wall layer development in a tribocharged fluidized bed

“…The total charge of the simulated bed is found to obey the exponential saturation model (Liao, Hsiau & Huang 2011;Pei, Wu & Adams 2016;Kolehmainen et al 2017a)…”

Effects of Polarization on Particle-Laden Flows

“…In this paper, we examine the effects of particle polarizability on particle-laden flow dynamics. We find that including polarizability produces new and distinct flow regimes in contrast to prior studies that have neglected polarization and consider only neutral or electrically charged particles [1][2][3][4][5][6][7][8][9][10]. Since the most pronounced effects of electrical charge are seen in insulating materials and since insulating materials tend to polarize, study of effects of polarization is relevant not only to flow and particle elutriation characteristics in gas-fluidized beds of particles [11,12], but also to a broad range of other applications involving charging of insulators.…”

Triboelectric charging of monodisperse particles in fluidized beds

“…The derivation of the formulas for a and b are given in Appendix A. Solving the ODE (22) for q with the initial conditions qð0Þ50 and Að0Þ50, and assuming that the contact area is independent of charge q(t) yields…”

“…As a result, studies in the literature on the effect of electrostatic forces on granular and gas-solid flows have either assumed a constant pre-specified level of charge on particles [14][15][16][17][18] or examined effective work function models for tribocharging. 7,[19][20][21][22][23] Laurentie et al 24 proposed an electron transfer model based on effective work function, and calibrated the effective work function by comparing discrete element method (DEM) simulations of tribocharging in a vibrated bed with experimental data. Essentially, the same electron transfer model was used in recent papers by Naik et al 20,25 to model tribocharging of pharmaceutical powders flowing in a chute.…”